The manufacture of tires typically involves a tire building drum wherein numerous tire components are applied to the drum in sequence, forming a cylindrical shaped tire carcass. This stage of the tire building process is commonly referred to as the “first stage” of the tire building process. The tire carcass is then typically removed from the tire building drum and sent to a second stage, expandable tire shaping drum where the carcass is expanded into a toroidal shape for receipt of the remaining components of the tire such as the belt package and a rubber tread. The completed toroidally shape unvulcanized tire carcass or green tire is then removed from the second stage drum and subsequently molded and vulcanized into a finished tire.
The prior art process thus requires two tire building drums and the transfer of the carcass from one drum to the other. Further, a problem often arises in precisely locating and anchoring the tire beads on the unvulcanized tire carcass, especially during the transportation of the tire beads from the first stage drum to the second stage drum. Variations in bead positioning can result in ply distortion in the tire.
Tire manufacturers have recently begun moving towards the utilization of a single tire building drum, for both the first and second stage tire building. This requires that the tire building drum be capable of axial expansion and contraction as well as radial expansion/contraction. Further, it is important to maintain a positive bead lock during the entire tire building process, including the tire shaping, so that the ply cord length is maintained, resulting in good tire uniformity. Due to the fact that the tire building drum axially and radially expands, it is important that both sides of the tire building drum move in synchronization. If one side of the drum is out of synchronization with the other side of the drum, problems in tire uniformity can occur. It is additionally desired to support the apex and bead assembly in a vertical manner while avoiding unwanted displacements of the tire components, particularly the ply.